Relationship between the inner intercanthal distance and the mesiodistal dimension of maxillary anterior teeth in a peruvian population with facial harmony.

: Objective: To determine the relationship between the inner intercanthal distance and the mesiodistal dimension of the maxillary anterior teeth in a Peruvian population with facial harmony. Material and Methods: A cross-sectional study on a sample of 75 Peruvian subjects with facial harmony, with ages ranging between 18 and 30 years, was conducted. The inner intercanthal distance and the mesiodistal dimension of maxillary anterior teeth of each subject were measured with a digital vernier caliper. The relationship was evaluated by simple linear regression analysis. Results: A statistically significant direct relationship was found between the dimension of the inner intercanthal distance with the mesiodistal width of the lateral incisors ( p =0.040, R2=5.65%), canines ( p =0.032, R2=6.17%), and the total mesiodistal sum of the six anterior teeth ( p =0.040, R2=5.63%), but not with the central incisors ( p =0.273, R2=1.64%). Conclusion: The inner intercanthal distance showed a direct relationship with the total mesiodistal linear dimension of the maxillary anterior teeth, with the mesiodistal dimensions of the lateral incisors and canines in a Peruvian population with facial harmony.


INTRODUCTION.
Maxillary anterior teeth play an important role in facial aesthetics.The shape, color and size of the teeth must be in harmony with the supporting facial structures. 1 The mesiodistal dimensions of teeth differ in each person due to a number of factors, 2 warranting the acquisition of individualized information for dental treatment. 3arious methods have been used to evaluate the relationship of the mesiodistal dimensions of the maxillary anterior teeth with certain facial structures. 4-6 Sayed et al., 7 concluded that intercomisural width and interalar width measurements are the only predictable methods to estimate the initial reference value for the width of anterior teeth.However, Gupta et al., 8 found a statistically significant relationship between the intercanine width with the inner intercanthal dimension and other facial measures, concluding that the inner intercanthal distance can be used as an anatomical reference for missing maxillary anterior teeth when they have been extracted.
Troncoso et al., 9 studied the relationship between intercanthal distance and width of upper anterior teeth in young Chilean subjects, finding a linear and proportional correlation between both variables.In contrast, Mishra et al., 10 studied the relationship between inner intercantal distance and other facial parameters with the combined width of the upper anterior teeth in two ethnic pospulations in Nepal, finding that intercanthal distance was not associated with the mesiodistal width of the upper anterior teeth.Similar results were found in an Indian population by Deogade et al., 1 The presence of these contradictory results in the literature and the lack of reports that evaluate the relationship of these variables in Peruvian subjects makes research in this population necessary.

MATERIALS AND METHODS.
The present cross-sectional study was conducted on a sample of 75 subjects between 18 and 30 years of age (21.28±3.75years), 33 females (21.24±3.23 years) and 42 males (21.31±4.15years).The subjects, residents of the cities of Trujillo and Cajamarca, Peru, attended to hospitals and universities in these locations, between the months of May and June 2018.The sample selection was for convenience, not probabilistic.Sample was calculated using the formula for correlation of variables, considering a statistical power of 95%, a confidence of 97.5% and a correlation of 0.463, obtained from data of a pilot study conducted in fifteen subjects.
The inclusion criteria were: subjects were at least third generation of Peruvian ancestry, with 6 healthy anterosuperior permanent teeth and clinical evidence of facial harmony (straight profile, with Glabela anglesubnasal (vertex).-Soft pogonion between 165º and 175º and lips at normal position in relation to the columella line-soft pogonion, distance of 0mm), central midline centered with the anterior teeth and chin, parallel bipupillary and commissural planes.The exclusion criteria were: subjects with moderate or severe dental crowding, using or having used orthodontic appliances, with a history of surgery or maxillary orthopedic procedures, anterior teeth with spacing, facial alterations and/or gingival inflammation.
The present research was approved by the Permanent Committee of Scientific Research, School of Stomatology of Antenor Orrego Private University (Code No.: 0177-2019-FMEHU-UPAO).Each participating subject signed an informed consent.The inner intercanthal distance was measured in millimeters, using a digital vernier caliper taking as reference from the right endocanth to the left.(Figure 1) To measure the mesiodistal dimensions of the upper incisors and canines, an impression was made of the upper arch with alginate (Tropicalgin-Zhermack, Mapledent Co., Guandong, China), using partial steel buckets.Dental casts were obtained immediately after the impression was taken, using type IV extra-hard plaster (Elite Rock, Fast-Zhermack, Badia Polesine, Italy).The largest mesiodistal dimension of each tooth was obtained, placing one end of the caliper on top of the curvature of the mesial face and the other end on top of the curvature of the distal face, parallel to the incisal surface.
The error of the method was evaluated in 15 subjects, making the measurements two weeks apart for intraexaminer calibration.Inter-examiner calibration was performed comparing the initial measurements performed by To evaluate the relationship between the intercanthal distance and the mesiodistal dimensions of the upper anterior teeth, simple linear regression analysis was used, considering the intercanthal width as an independent variable.A level of significance of 5% was considered.

DISCUSSION.
The data of the present study suggest that there is a relationship between the inner intercanthal distance and mesiodistal dimension of upper anterior teeth in a Peruvian population with facial harmony.These results differ from those reported by Mishra et al., 10 who found no relationship between the variables under study in Nepal, and those of Deogade et al., 1 in an Indian population.
For Deogade et al., 1 intercanthal distance cannot be used as a preliminary method to determine the width of the upper anterior teeth since Pearson's correlation coefficients were relatively small.However, based on the results of this study, where a significant relationship was found, it would be feasible to predict the total sum of the anterior teeth, of the canines and lateral incisors from the intercanthal dimension, using simple linear regression models.
Troncoso et al., 9 calculated the dimension of the upper anterior teeth using the intercanthal distance in a young adult population in southern Chile, proving this to be a reliable prediction guide.Similar results were found in the present study, and the individuals who participated in this study also of South American origin.
A limitation of the present study is the univariate analysis performed.It is suggested to conduct more studies assessing the intervention of other variables in this relationship.Likewise, having selected the sample for convenience limits the extrapolation of the results.However, since the subjects evaluated have facial harmony, these results can be used as a guide for diagnosis and treatment planning.On the other hand, one of the greatest advantages of inner intercanthal distance is dimensional stability over time, which becomes an advantage for the clinician, since it could be taken as a reference to estimate the mesiodistal dimensions of the upper anterior teeth in the rehabilitation plan.
The results of the present study suggest that given the direct relationship found, intercanthal distance could be used as a reference for the rehabilitation of the maxillary anterior teeth.However, further studies in other populations are needed.

CONCLUSION.
There is a direct relationship between the inner intercanthal distance with the total mesiodistal linear dimension of the maxillary anterior teeth, with the mesiodistal dimensions of the lateral and canine incisors in a Peruvian population with facial harmony.

Figure 1 .
Figure 1.Schematic representation of the inner intercanthal distance measurement.

Saldaña-Carranza V & Carruitero MJ.
Relationship between the inner intercanthal distance and the mesiodistal dimension of maxillary anterior teeth in a peruvian population with facial harmony.J

Table 1 .
Relationship between the inner intercanthal distance and the mesiodistal width of the upper anterior teeth in Peruvian subjects with facial harmony (n=75).